The present invention relates to swirl-chamber Diesel engines.
Swirl-chamber Diesel engines comprise a cylinder block, a piston reciprocally disposed in a cylinder of the cylinder block, a cylinder head secured to the cylinder block and closing the cylinder, a main combustion chamber formed in the cylinder between the piston and the cylinder head, a generally spherical swirl chamber formed in the cylinder head and a communication passage formed in the cylinder head to establish communication between the main and auxiliary combustion chambers. The communicating passage connects tangentially into the swirl chamber so that during the compression stroke of the piston part of air charge in the main combustion chamber flows into the swirl chamber along a line tangent to the wall thereof to generate swirl therein. A fuel injection nozzle is mounted to the cylinder head and opens into the swirl chamber. Within the swirl chamber a shoulder is formed around the port of the passage at which the passage opens into the swirl chamber and located on the opposite side to the side along which air flows into the swirl chamber from the communicating passage during the compression stroke of the piston. The injection nozzle points toward the shoulder so as to direct jet of fuel toward and along the swirl of air in the swirl chamber such that the jet of fuel will not enter directly into the main chamber through the communicating passage. A heater plug or glow plug extends into the swirl chamber to produce heat close to the jet of fuel to give a starting aid. The piston is formed at its crown with a depression of a spherical design. This depression, when the piston is on its top dead center, forms part of the complete combustion chamber. It consists of cup-shaped cavities communicating at their junctions with the swirl chamber. By dividing the subsequent combustion gases flow from the passage into two streams flowing around the cup-shaped cavities some degree of air swirl during combustion is generated outside the swirl chamber; this encourages the feeding of fresh air to the emerging fuel.
In regard to operation of the Diesel engine constructed as above, during the compression stroke of the piston, the air charge in the main combustion chamber is compressed so that part thereof flows into the swirl chamber through the communicating passage thereby to generate swirl therein so as to be compressed to produce a heat zone at the center of the swirl. The jet of fuel from the fuel injector or injection nozzle is directed into the swirl to be ignited by the heat generated by the swirl. The subsequent combustion gases flow into the main combustion chamber from the communicating passage to effect diffusion burning.
In operation, when the engine, as constructed above, runs at low engine speed, such as, when the engine is idling, the swirl of air within the swirl chamber is weak and not strong enough so that the fuel injected from the nozzle will not mix well with the air. The fuel droplets, therefore, tend to adhere to the swirl chamber wall, flowing along the wall of the passage into the main combustion chamber, thus likely to result in ignition within the main combustion chamber and in knockings.